Process for producing spherical zeolite catalyst and apparatus for producing the same

ABSTRACT

A process for producing a spherical zeolite catalyst is disclosed, which comprises dropping a zeolite-containing alumina sol into a surfactant-containing oil phase from a dropping opening directly or through air to thereby form spherical droplets of the sol, and then allowing the droplets to gel in an aqueous alkaline solution phase underlying the oil phase and withdrawing the thus gelled droplets, said dropping of the sol being conducted while the dropping opening is being impulsed to thereby impart a spherical and uniform shape to the resulting zeolite particles containing alumina as a binder, and a novel apparatus therefor.

This is a divisional of application Ser. No. 07/849,346 filed Mar. 11,1992 now U.S. Pat. No. 5,362,696.

FIELD OF THE INVENTION

The present invention relates to a process for producing a sphericalzeolite catalyst having high strength and to a novel apparatus forproducing the catalyst.

BACKGROUND OF THE INVENTION

Spherical particles of alumina, silica, silica-alumina, zeolite, and thelike are extensively used, for example, as catalyst supports, dryingagents, and adsorbents in the chemical industries, including petroleumchemistry and petroleum refining. When used as a catalyst, sphericalparticles having diameters of about from 0.5 to 5 mm are packed in areactor called a fixed bed or moving bed. Because of their sphericalshape, the particles readily flow, making charging and discharging ofthe catalyst easy. Further, since such a spherical catalyst is chargeduniformly, no particular technique is required for the charging, andchannelling or abnormal flow is less apt to occur during reaction, whichcontributes to safe operation. For use in the moving bed reactors whichare of the type in which a catalyst bed gradually moves downward due toits own weight, an essential requirement of the catalyst particles is aspherical shape.

Such spherical catalysts are produced by a "dropping-into-oil" method asdescribed, for example, in JP-B-26-4113, JP-B-54-163798, JP-B-38-17002and JP-B-11-6771, or by a "rolling-and-moving" method as described, forexample, in JP-B-52-14720 and JP-B-55-29930. (The term "JP-B" as usedherein means an "examined Japanese patent publication".)

The dropping-into-oil method can produce spherical particles which arerelatively uniform and nearly truly spherical. The rolling-and-movingmethod yields spherical particles which have a broad diameterdistribution and are not so truly spherical, but this method is beingextensively employed because of the low production costs involved.Spherical particles for use in moving beds are required not only todescend by their own weight, but to have such properties or performancesas uniform size, a nearly true spherical shape, surface smoothness, highstrength, high abrasion resistance and the like, because the catalyst istransferred in an air stream for regeneration. For this reason, thespherical particles for use as moving bed catalysts have been producedby the dropping-into-oil method.

In producing a spherical alumina catalyst by the conventionaldropping-into-oil method, a reagent which decomposes at hightemperatures to evolve ammonia, such as hexamethylenetetramine or urea,is used, and an alumina sol is caused to gel by alkalinity. It is,therefore, necessary, according to this method, that an alumina sol bedropped into a high-temperature oil having a temperature close to 100°C. and that the resulting sol droplets be aged for as long as more than20 hours. After being thus aged in the oil and then washed, theresultant particles are required to further undergo a post-treatment inwhich they are immersed in an aqueous solution of ammonium chloride orin ammonia water for several hours in order to increase their strength.If a spherical zeolite catalyst containing alumina as a binder is to beproduced by this method, a long gelation time is required and thiscauses a problem in that the particles being produced are prone tocoalescence, deformation, or breakage, leading to a low product yield.In addition, since the only technique for controlling the dropletdiameters is to change the diameter of the dropping opening, it has beendifficult to freely control droplet diameters and to cope with anyviscosity change of the raw material due to a change in zeoliteproportion. Furthermore, although spherical zeolite catalysts arerequired to contain a zeolite, the active ingredient, in a proportion ashigh as possible in order to have a high catalytic activity per unitweight, there is the problem that the larger the zeolite content, thelower the catalyst particle strength.

SUMMARY OF THE INVENTION

The present inventors have made extensive studies in order to eliminatethe above-described problems. As a result, they have succeeded indeveloping a dropping-into-oil method by which a spherical zeolitecatalyst having high strength can easily be produced in a large quantityand high yield within a short time period, and also succeeded indeveloping a zeolite particle-drying technique and a spherical zeolitecatalyst-producing apparatus for practicing the above method. Thepresent invention has been completed based on the above.

Accordingly, the present invention provides, in one aspect thereof, aprocess for producing a spherical zeolite catalyst, which comprisesdropping a zeolite-containing alumina sol into an oil phase from adropping opening directly or through air to thereby form sphericaldroplets of the sol, and then allowing the droplets to gel in an aqueousalkaline solution underlying the oil phase, the dropping of the solbeing conducted while the dropping opening is being impulsed to therebyimpart a uniform shape to the resulting zeolite particles containingalumina as a binder.

The present invention further provides, in another aspect thereof, anapparatus for producing a spherical zeolite catalyst, which comprises areaction vessel for containing an oil phase as an upper layer and anaqueous alkaline solution phase as a lower layer, a dropping meanshaving a dropping opening for feeding a raw material to the reactionvessel (liquid tank), and an impulse generating means or "knocker" forimpulsing the dropping opening. The .impulse generating means or"knocker" employed is not particularly limited in construction thereofso long as it functions to give a constant-strength impulse to thedropping opening at regular time intervals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic front view of one embodiment of the apparatusof the present invention for producing a spherical zeolite catalystwherein 1 donates a raw material tank, 2 donates dropping openings, 3donates an oil phase, 4 donates an interface between an oil phase and anaqueous alkaline solution phase, 5 donates an aqueous alkaline solutionphase, 6 donates an outlet, 7 donates an impulse generating means, 8donates an impulse generating regulator (or pressure regulator), 9donates a spout, 10 donates an aqueous alkaline solution circulatingpump, 11 donates a suction port, 12 donates an impulse receiving means,and a donates a surface in a case where droplets are dropped throughair; and

FIG. 2(A) to 2(C) present diagrammatic front views illustrating threekinds of dropping openings that can be employed in the spherical zeolitecatalyst-producing apparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The construction and effects of the present invention are explainedbelow with reference to FIG. 1.

Raw material fed from a raw material tank 1 is dropped into an oil phase3 through dropping openings 2. The raw material-dropping means has beenprovided thereover with an impulse generating means or "knocker" 7,which impulses the dropping openings; in FIG. 1, the impulse generatingmeans or "knocker" 7 is actuated by pressurized air from the impulsegenerating regulator 8. The impulse strength and interval betweenimpulses are properly determined according to the properties of the rawmaterial sol. After the dropping into the oil, the resulting droplets(not shown) of the zeolite-containing alumina sol descend through theoil phase while becoming spherical. The sol droplets that have becomespherical pass through an interface 4 between the oil phase and anaqueous alkaline solution phase 5 to enter the aqueous alkaline solutionphase. The droplets further descend through the aqueous alkalinesolution phase, which is typically water which has been renderedalkaline, while gradually gelling and solidifying from the surfacesthereof, and the solidified particles are withdrawn from outlet 6 at thebottom of the reaction vessel.

In the case where the raw material sol is dropped from the droppingopenings 2 of the nozzles into the oil phase directly or through airwithout impulsing the openings, the resulting gel droplets have acertain diameter which is determined by the interfacial tension betweenthe raw material sol and the oil phase, the adhesion of the sol to theedges of the dropping openings, the density and the viscosity of thesol, and other factors. In this case, it is considered that the dropletsize becomes smaller as the interfacial tension becomes higher, theadhesion lower, the density higher, and the viscosity lower. Therefore,a change in the properties of the raw material results in a change indroplet diameter. Changes in raw material properties can be attended toby impulsing the dropping openings. For example, if the viscosity of theraw material increases, a constant droplet diameter can be maintained byincreasing the strength of the impulses and by extending the intervalsbetween impulses.

In dropping through air, arbitrary range of the distance between theopenings and the oil phase is acceptable so long as droplets are notdistructed, and it is generally not more than 1 m.

The impulse generating means or "knocker" is not particularly limited instructure so long as it functions to give a constant-strength impulse tothe dropping openings at regular time intervals, and any of variouskinds of "knockers" may be used. Examples of the "knockers" include anair "knocker" operated by air pressure, a mechanical "knocker" operatedby an electric motor, an electromagnetic "knocker" utilizing magneticforce, and the like. When a part of the sol has come out of a droppingopening into the oil or air but is still clinging to the nozzle, the"knocker" impulses the dropping means and the impulse is transferred tothe whole nozzle to abruptly vibrate the dropping opening, whereby thatpart of the sol becomes free and falls by gravity. According to thistechnique, by suitably setting both the impulse strength for the"knocker" and the impulse intervals, it is possible to form sol dropletshaving an arbitrary diameter up to the diameter of sol droplets formedby free dropping.

The zeolite-containing alumina sol used as the raw material is notparticularly limited so long as spherical droplets can be formedtherefrom. However, a preferred example thereof is a zeolite-containingalumina sol which has been prepared by mixing an alumina sol containingfrom 5 to 30% by weight of boehmite or pseudoboehmite with a zeolite insuch proportions as to result in a zeolite content of from 5 to 90% byweight in terms of dry zeolite content in the zeolite-containing aluminasol and which has a viscosity of from 50 to 3,000 cSt. It is preferredto use an alumina zol which has been stabilized using acetic acid ion,chlorine ion, nitrate ion, and the like.

The dropping opening in each nozzle is not particularly limited so longas its horizontal cross section is circular. Exemplary nozzle typesinclude a syringe needle type (FIG. 2(a)), an injection nozzle type(FIG. 2(b)), and a normal opening type (FIG. 2(c)) as shown in FIG. 2,but other various types may be used in the present invention. One of thefeatures of the present invention resides in that dropping of the rawmaterial is independent of the shape of the dropping opening and soldropping from any of the dropping openings shown in FIG. 2 proceedssatisfactorily. Further, the number of dropping openings can be easilyincreased, and from several hundreds to several thousands droppingopenings may be formed so long as impulse control is possible. Thedropping of the raw materials is independent of the dropping opening solong as the dropping opening is circular in cross-section.

It is preferred that the inner diameter of the dropping opening at thetip thereof be in the range of from 0.5 to 3 mm, although this rangevaries depending on raw material properties and desired particlediameters.

With respect to the properties of the oil, the viscosity and densitythereof are important. If the oil has too high a viscosity, sol dropletsare deformed before gelling into a perpendicularly extended shape due tothe viscosity of the oil. If the oil has too low a density, sol dropletsdescend at an increased speed, so that they assume a disk form becauseof increased oil resistance. Therefore, the oil should have a viscosityand density suited for the properties of the sol droplets. In thepresent invention employing a zeolite-containing alumina sol as the rawmaterial, the preferred ranges of the density and viscosity of the oilphase are from 0.6 to 0.9 g/cm³ and from 1 to 3 cSt, respectively.Specific examples of the oil phase include petroleum fractions such askerosine and light oil, organic solvents such as hexane, and othervarious hydrocarbons. The term "oil phase", this simply means an "oil"and preferably a surfactant. The residence time of the droplets in theoil phase is generally 0.5 to 50 seconds for sphering droplets.

Due to the interfacial tension between the oil phase and the aqueousalkaline solution phase, the sol droplets which have descended throughthe oil phase make a short stop at the interface. Usually, this does notaffect particle formation because the droplets stay there only for ashort time period in most cases. However, if the droplets stay at theinterface for a prolonged time period, there can be the case thatgelation begins in those parts of the droplets which are below theinterface and in contact with the aqueous alkaline solution phase, sothat each droplet gels nonuniformly, and, at the same time, adhesionbetween droplets occurs on the oil phase side where gelation has notbegun, resulting in nonuniform particles. Such problems can beeliminated by adding a surfactant to the oil phase and/or the aqueousalkaline solution phase to lower the interfacial tension between the twophases, thereby enabling the sol droplets to readily pass through theinteface and preventing them from staying there for an unacceptableperiod of time. For this purpose, any surfactant may be used so long asit enables the droplets of the zeolite-containing alumina sol to passsmoothly through the interface without staying there for an unacceptableperiod of time. This surfactant may be an oil-soluble surfactant, awater-soluble surfactant, or a combination of both. Various oil-solublesurfactants may be used in the present invention. However, in order toproduce spherical zeolite particles for use as a catalyst, theoil-soluble surfactant is preferably a nonionic surfactant whichcontains no alkali metal or sulfuric acid radicals, is removable bycalcination to exert no influence on the product, and has an HLB valueof from 3 to 10, preferably from 4 to 7. Further, since the surfactantincorporated in the oil phase also affects the droplets that aredescending through the oil phase, a lower surfactant concentration ispreferred so long as the smooth passage of the droplets through theinterface is possible. Specifically, the preferred range of thesurfactant concentration in the oil phase is from 0.01 to 2.0% by weightbased on the oil itself. A water-soluble surfactant has the same effect.The term "aqueous alkaline solution phase", this simply means water plusa base and optionally a surfactant.

Another technique for preventing the coalescence or deformation of soldroplets due to their stay at the interface between the two phases is toshake the interface to a proper degree. This also is an effective means.When the interface is being shaked, the sol droplets are kept dispersedat the interface and, at the same time, pass through the interfacewithin a reduced time period due to the vibration of the interface.Shaking of the interface may be attained by stirring the oil phase oralkaline aqueous solution phase at the interface. In the apparatus ofFIG. 1, the alkaline aqueous solution phase is circulated in order toshake the interface and also for the purpose of taking out particlesthat have gelled. In this case, the alkaline aqueous solution phase maybe jetted either from a spout 9 disposed near the interface or in adirection parallel or perpendicular to the interface. Alternatively, theliquid tank may be provided with a screw near the interface tomechanically shake the interface by revolving the screw. Other varioustechniques may be utilized for shaking the interface.

The aqueous alkaline solution phase is preferably one which has a pHvalue of from 9 to 11 and will not remain on the product. An aqueoussolution of ammonia is usually employed as the alkaline aqueous solutionphase. Ammonia concentration affects gelation time. If the ammoniaconcentration is too low, the sol droplets reach the bottom of the tankbefore the surfaces thereof gel sufficiently, causing the resultingparticles to suffer deformation or coalescence. If the ammoniaconcentration is too high, gelation of each droplet proceedsnonuniformly because only the surface of the droplet gels too quickly,resulting in impaired product strength. A proper range of the ammoniaconcentration in the aqueous phase is from 0.2 to 20% by weight based onwater plus ammonia, with the preferred range thereof being from 2 to 10%by weight based on water plus ammonia.

The apparatus of the present invention for producing a spherical zeolitecatalyst is explained below with reference to FIG. 1. This apparatus ischaracterized as comprising a reaction vessel capable of containing anaqueous alkaline solution phase 5 and an oil phase 3, a nozzle having adropping opening 2 for dropping a raw material therethrough from a rawmaterial tank 1 into the oil phase in the reaction vessel, and animpulse generating means 7 disposed over the nozzle and having animpulse generating means regulator 8 for regulating impulse strength andimpulse intervals. desired, a spout or injection nozzle 9 for jettingthe oil phase or aqueous alkaline solution phase may be disposed nearthe interface 4 between the oil phase and the alkaline aqueous solutionphase. In the case where this spout 9 is for jetting the oil phase, itis preferably positioned above the interface between the two phases.Where the spout 9 is for jetting the alkaline aqueous solution phase, itis preferably positioned below the interface. By jetting the oil phaseor aqueous alkaline solution phase from the spout, the interface iscaused to vibrate up and down and, as a result, sol droplets can be keptdispersed and pass through the interface in a reduced time period.Further, part of the aqueous alkaline solution phase may be circulatedand jetted from the spout 9. The spherical particles thus formed in theapparatus of FIG. 1 are withdrawn from outlet 6 of the apparatus at thebottom thereof and then aged in an aqueous alkaline solution for aperiod of from several minutes to ten-odd (about ten) hours in order toallow gelation to proceed sufficiently. Generally, the aging isconducted at pH of 9 to 11 under atmospheric pressure at normaltemperature. The resulting particles are then taken out, dried, and thencalcined.

The present invention further provides, according to still anotheraspect thereof, a process for producing a spherical zeolite catalyst,which comprises dropping a zeolite-containing alumina sol into an oilphase directly or through air to thereby form spherical droplets of thesol, allowing the droplets to gel in an aqueous alkaline solution phaseunderlying the oil phase, and drying and then calcining the resultinggel particles to thereby obtain a spherical zeolite catalyst containingalumina as a binder, the drying being conducted at a temperature below100° C. to thereby impart a higher strength and truly spherical anduniform shape to the catalyst particles.

In the above process, the dropping of a zeolite-containing alumina solinto an oil, which is performed directly or through air, may be carriedout by any method so long as the dropping method used can form soldroplets having a constant diameter. For example, the zeolite-containingalumina sol may be allowed to freely fall dropwise into an oil phasedirectly or through air from dropping openings having the same diameter.Alternatively, a technique of mechanically regulating the diameter ofsol droplets may be used.

The compositions and properties of the oil phase and aqueous alkalinesolution phase for use in forming spherical sol droplets in this processpreferably are as described hereinabove.

In the spherical sol droplets, gelation proceeds from the surface to theinner part of each droplet. Although the mechanism of this gelation hasnot been fully elucidated, it is believed that hydrated aluminumhydroxide undergoes a dehydration condensation to form a polymericnetwork structure. In each spherical droplet, its surface in contactwith the aqueous alkaline solution gels and solidifies relativelyrapidly, but gelation of the inner part of the droplet requires moretime because the aqueous alkaline solution phase must diffuse into theinner part through spaces within the network structure. Therefore, it isnecessary to age and solidify the resulting spherical particles in anaqueous alkaline aging solution for a certain time period in order toprevent the particles from undergoing coalescence or deformation inpost-treatment. In the case of spherical particles having a diameter of1.5 mm, 20 hour aging in a 5% alkaline solution is still insufficientfor the gelation of the inner parts of the particles. However, it hasbeen found that complete gelation in an aqueous alkaline solution isunnecessary for the formation of true spherical catalyst particles withhigh strength and that shorter aging times are preferred so long as theparticles do not suffer coalescence or deformation in the subsequentdrying. Although the aging time varies depending on the concentration ofthe aqueous alkaline aging solution, it is generally from 5 minutes to10 hours, preferably from 30 minutes to 5 hours, when the aqueoussolution is 1 to 10% aqueous ammonia. Why shorter aging periods arepreferred is not clear, but it can be considered that the aging time mayaffect the shrinkage of the aged particles in the subsequent drying.

The spherical particles the surfaces of which have gelled and which havesolidified to a degree sufficient for avoiding coalescence anddeformation are separated from the aqueous alkaline aging solution byfiltration, and then dried. In this drying step, the spherical particlesgradually shrink, due to loss of water, to a size having a diameterabout from 2/3 to 1/2 of that before drying and a volume about from 1/3to 1/10 of that before drying. In the drying of an ordinary solidparticle, it is considered that the water present around the particlesurface first evaporates and the surface becomes dry, the waterremaining inside then diffuses to the surface through minute pores, andthe inner part is thus dried gradually. In the case drying the sphericalparticles according to the process of the present invention, it isconsidered that with the progress of the drying, the water is graduallyeliminated and the volume of each particle decreases at a ratecorresponding to the water elimination. It is considered to be cruciallyimportant that the aluminum hydroxide contained in the particles shouldbe prevented, throughout the drying, from undergoing a chemical changedue to a dehydration condensation to form a strong gel structure and tothereby stop the shrinkage of the particles. In order to inhibit thischemical reaction, a lower drying temperature and a shorter drying timeare preferred. In order to efficiently eliminate the water from theparticles, it is preferred to flow a gas around the particles to reducethe thickness of laminar sublayers so as to lower diffusion resistanceas much as possible, and that, as this gas, a low humidity gas obtainedby moisture removal should be used for the purpose of increasing, asmuch as possible, the moisture concentration gradient in the gas phasein contact with the particle surfaces.

The drying gas is preferably an inert gas such as helium, nitrogen, air,carbon dioxide gas, or the like. Of these, helium is most preferred inthat the use of helium gas, which is the lowest in viscosity among thosegases, results in thin laminar sublayers and, hence, provides thehighest drying rate. However, helium is expensive, and dry air isusually sufficient.

The drying is carried out by causing a dry gas regulated to have a lowrelative humidity to flow around the spherical particles at atemperature below 100° C. to above 0° C. The lower the humidity of thegas, the higher the drying rate. However, a moisture containing gashaving a humidity up to around 80% RH can be used if the flow speed ofthe gas is high. Drying rate increases with increasing dryingtemperature, because the vapor pressure of water rises from 9 mmHg at10° C. to 23 mmHg at 25° C. and to 93 mmHg at 50° C. However, sincehigher drying temperatures accelerate chemical gelation to yieldcatalyst particles having impaired strength, a proper drying temperatureis determined by the required catalyst strength.

In the case where drying is conducted by allowing the sphericalparticles to stand without a low-humidity gas flow, the drying time isrequired to be from 8 hours to 2 days at 20° C. and from 2 to 8 hours at80° C. In contrast, in the case of drying with a low humidity gas flow,the drying time can be reduced greatly, i.e., it is 30 minutes to 2hours at 20° C. and several minutes to 1 hour at 80° C. Besidesachieving such a drying time reduction, the gas flow drying also has theeffect of increasing the catalyst strength by about 10 to 20%. It isnoted that the conventionally employed drying at temperatures not lowerthan 100° C. is disadvantageous in that the products have low catalyststrength, although the drying time is short.

Catalyst strength herein means the strength of a catalyst particle asdetermined with a Kiya-type strength meter. This strength meter measuresthe crushing strength of a particle and the strength value obtainedindicates the load resistance of the particle. In the case of catalystparticles containing alumina as a binder, larger crushing strengthvalues obtained with the strength meter not only indicate higher loadresistance, but show higher abrasion and impact resistance. Hence, suchcrushing strength values are extensively used as a measure of catalystperformance.

As the drying apparatus, use may be made of a batch drying apparatus inwhich the material to be dried is kept stationary, such as thatdescribed in Chemical Engineering Handbook, edited by ChemicalEngineering Society, Japan, 1988, p. 673, or a continuous hot air dryingapparatus in which the material to be dried is transferred, such as thatdescribed on p. 674 of that Handbook. With such apparatus, the sphericalparticles can be treated in a large quantity within a short time period.

After the drying, the spherical particles are calcined. This calcinationmay be conducted at 550° C. for 3 hours. Thus, a spherical zeolitecatalyst of the present invention is obtained. The shape of eachspherical particle changes little through the calcination.

According to the process of the present invention, a spherical zeolitecatalyst is produced in significantly improved yield because gelation inan aqueous alkaline solution phase can be conducted at ordinarytemperature in a short time period. Further, it has become possible toproduce a spherical zeolite catalyst having a high zeolite content andhigh strength in a large quantity within a short time period.

That is, by impulsing the dropping openings, droplet diameter controlhas become possible over a wide range of raw material viscosities.Moreover, most especially by adding a surfactant to the oil phase,production of nearly true spherical zeolite particles has become easy.Furthermore, by shaking the interface between the oil phase and thealkali containing aqueous solution phase, further improved product yieldand further improved sphericity have been attained.

As a result, it has become possible, according to the process of thepresent invention, to produce spherical zeolite catalyst particles whichare highly precise in size from a wide range of raw materials in highyields within short time periods.

According to the apparatus of the present invention, the process forproducing spherical zeolite catalyst particles can be easily practicedunder optimum conditions for dropping of the raw material and forshaking of the interface between the two phases and, hence, theabove-described effects can easily be brought about.

The present invention will be explained below in more detail withreference to the following examples, but the invention is not construedas being limited thereto.

EXAMPLE 1

Three kinds of mixtures were prepared by mixing a commercially availablealumina sol (manufactured by Nissan Chemical Industries, Ltd., Japan)having an alumina content of 10% by weight (based on total sol weight)with a pentasil-type zeolite in such proportions that the resultingmixtures had alumina:zeolite ratios of 30:70, 50:50, and 70:30 byweight, respectively, on a dry basis. The three mixtures are referred toas raw materials A, B, and C, respectively. The viscosities of rawmaterials A, B, and C were 1,000 cSt, 600 cSt, and 400 cSt,respectively. Each of raw materials A, B, and C was fed separately tothe raw material tank as shown in FIG. 1, and dropped directly into anoil by pressurizing the raw material tank. As the nozzles, those havingdropping openings of the type as shown in FIG. 2 were used. The droppingopenings had an inner diameter of 1 mm. As the impulse generating means,an air knocker manufactured by Hayashi Vibrator, Japan was used. Theimpulse generating means was regulated to give an impulse at a frequencyof 2 times per second. The impulse strength was changed according to rawmaterial viscosity by controlling the air pressure applied thereto. Thatis, for raw materials A, B, and C, the air pressures applied to theknocker were 2.9 kg/cm² G, 2.6 kg/cm² G, and 2.3 kg/cm² G, respectively.

The liquid phase of a reaction vessel was 1.5 m in length, in which theoil phase was 1 m and the aqueous alkaline phase was 0.5 m. The oilphase (density 0.794 g/cm³ at 15° C. and 1.5 cSt at 30° C.) contained1.0% by weight (based on oil plus surfactant) of a nonionic surfactant(a polyoxyethylene alkylphenyl ether) having an HLB value of 6. Theaqueous alkaline solution phase underlying the oil phase contained 5% byweight of ammonia (based on water plus ammonia). The oil and aqueusphases were normal temperature and normal pressure. The sol dropletsresulting from the dropping of each of the zeolite-containing aluminasols descended without staying at the interface (the time at theinterface was less than 0.5 second) between the oil and aqueous phasesand settled on an accumulation means above the outlet at the bottom ofthe apparatus, where the shape of each resulting particle was keptspherical and the particles were kept separate. The residence time inthe oil phase was 4 seconds. The spherical particles withdrawn from thereaction vessel were aged in 5% aqueous ammonia for 12 hours,subsequently dried by being allowed to stand at 120° C. under ambientpressure for 3 hours, and then calcined at 550° C. under ambientpressure in air for 3 hours. Thus, a spherical zeolite catalyst having ahigh sphericity degree and high strength was obtained from each of rawmaterials A, B, and C.

The results of property measurements of the thus-obtained catalysts aresummarized in Table 1.

EXAMPLE 2

A raw material mixture was prepared by mixing a commercially availablealumina sol (manufactured by Nissan Chemical Industries, Ltd.) having analumina content of 20% by weight with a pentasil-type zeolite in suchproportions that the resulting mixture had an alumina:zeolite ratio of30:70 by weight on a dry basis. This mixture is referred to as rawmaterial D. The viscosity of raw material D was 800 cSt. The same nozzleand knocker as those in Example 1 were used. The knocker was regulatedto give an impulse at a frequency of 2 times per second, and the airpressure applied to the knocker was 2.0 kg/cm² G. The oil used contained0.5% by weight of a nonionic surfactant (a sorbitan fatty acid ester)having an HLB value of 4. Except the above, the same procedures as inExample 1 were conducted, thereby obtaining a spherical zeolite catalysthaving a high sphericity degree and high strength.

EXAMPLE 3

A boehmite alumina powder was added to a commercially available aluminasol (manufactured by Nissan Chemical Industries, Ltd.) having an aluminacontent of 20% by weight to prepare an alumina sol having an aluminacontent of 30% by weight. There was mixed therewith a pentasil-typezeolite in such proportions that the resulting mixture had analumina:zeolite ratio of 50:50 by weight on a dry basis. This mixture isreferred to as raw material E. The viscosity of raw material E was 2,000cSt. The same nozzle and knocker as those in Example 1 were used. Theknocker was regulated to give an impulse at a frequency of 1.5 times persecond. The air pressure applied to the knocker was 2.5 kg/cm² G. Exceptfor the above, the same procedures as in Example 1 were conducted,thereby obtaining a spherical zeolite catalyst having a high sphericitydegree and high strength.

EXAMPLE 4

A boehmite alumina powder was added to a commercially available aluminasol (manufactured by Nissan Chemical Industries, Ltd.) having an aluminacontent of 20% by weight to prepare an alumina sol having an aluminacontent of 30% by weight. There was mixed therewith a pentasil-typezeolite in such proportions that the resulting mixture had analumina:zeolite ratio of 30:70 by weight on a dry basis. This mixture isreferred to as raw material F. The viscosity of raw material E was 2,800cSt. The same nozzle and knocker as those in Example 1 were used. Theknocker was regulated to give an impulse at a frequency of 1.5 times persecond. The air pressure applied to the knocker was 3.5 kg/cm² G. Exceptfor the above, the same procedures as in Example 1 were conducted,thereby obtaining a spherical zeolite catalyst having a high sphericitydegree and high strength.

EXAMPLE 5

The same procedures as in Example 1 were conducted except that rawmaterial A only was used and that in place of the nonionic surfactant, asodium alkylbenzenesulfonate was added to the aqueous alkaline solutionphase in an amount of 0.1% by weight. A spherical zeolite catalysthaving a high sphericity degree and high strength was thus obtained.

EXAMPLE 6

The same procedures as in Example 5 were conducted except that rawmaterial A was dropped into the oil through air. A spherical zeolitecatalyst having a high sphericity degree and high strength was thusobtained. The distance between the opening and the oil was 30 cm.

COMPARATIVE EXAMPLE 1

Each of raw materials A, B, and C was dropped directly into an oilwithout giving an impulse to the nozzle by the knocker. As a result, thesol droplets had diameters about two times that of the droplets formedwith the application of impulses, and particle diameter control was notattained.

COMPARATIVE EXAMPLE 2

The same procedures as in Example 1 were conducted except that rawmaterial A only was used and no surfactant was added to the oil. As aresult, the sol droplets stayed at the interface between the oil andaqueous phases and underwent coalescence. Therefore, the product yieldwas very low.

                                      TABLE 1                                     __________________________________________________________________________                           Ex- Ex- Ex- Ex- Ex-                                                           ample                                                                             ample                                                                             ample                                                                             ample                                                                             ample            Comparative                      Example 1   2   3   4   5   6   Comparative Example                                                                        Example               __________________________________________________________________________                                                            2                     Raw material                                                                             A   B   C   D   E   F   A   A   A   B    C   A                     Drying     120 120 120 120 120 120 120 120 120 120  120 120                   temperature, °C.                                                       Drying time, hr                                                                          3   3   3   3   3   3   3   3   3   3    3   3                     Product yield, wt %                                                                      96  97  96  97  97  96  97  96  98  98   98  62                    Average particle                                                                         1.4-1.6                                                                           1.4-1.6                                                                           1.4-1.6                                                                           1.4-1.6                                                                           1.4-1.6                                                                           1.4-1.6                                                                           1.4-1.6                                                                           1.4-1.6                                                                           2.8-3.5                                                                           2.7-3.2                                                                            2.5-3                                                                             1.4-1.6               diameter, mm                                                                  Average    0.9-1.6                                                                           1.9-3                                                                             2.4 -3.9                                                                          1.4-2.1                                                                           2.5-3.6                                                                           1-1.8                                                                             0.9-1.7                                                                           0.8-1.7                                                                           3.2-4.4                                                                           4.2-5.7                                                                            5.1-6.6                                                                           0.9-1.5               strength, kg                                                                  Average    1.01                                                                              1.011                                                                             1.008                                                                             1.012                                                                             1.009                                                                             1.013                                                                             1.009                                                                             1.010                                                                             1.10                                                                              1.11 1.25                                                                              1.07                  sphericity degree                                                             __________________________________________________________________________     ##STR1##                                                                      ##STR2##                                                                     ?                                                                              ##STR3##                                                                     ?                                                                         

EXAMPLE 7

Using each of raw materials A and C, spherical particles that hadundergone surface gelation were prepared in the same manner as inExample 1. The spherical particles formed from each of raw materials Aand C and withdrawn from the reaction vessel were aged for 2 hours in 5%aqueous ammonia to allow the particles to gel sufficiently, subsequentlyplace in an air flow type drying apparatus, and then dried byintroducing air having a humidity of 10% RH under three conditions,i.e., 80° C.--20 minutes, 50° C.--40 minutes, and 20° C.--1 hour.Thereafter, the dry particles were calcined at 550° C. in air for 3hours, thereby obtaining spherical zeolite catalysts having highsphericity degrees and high strengths. The results of propertymeasurements of these catalysts are shown in Table 2.

EXAMPLE 8

The same procedures as in Example 7 were conducted except that rawmaterial A only was used and drying was conducted at 20° C. for 2 hoursusing air regulated to have a humidity of 60% RH, thereby obtaining aspherical zeolite catalyst having a high sphericity degree and highstrength.

EXAMPLE 9

The same procedures as in Example 7 were conducted except that rawmaterial A only was used, that the aqueous alkaline solution phaseemployed was one prepared by adding, in place of the nonionicsurfactant, 0.1% by weight of a sodium alkylbenzenesulfonate to 8 wt %aqueous ammonia, and drying was conducted at a humidity of 50% RH and atemperature of 50° C. for 1 hour. Thus, a spherical zeolite catalysthaving a high sphericity degree and high strength was obtained.

EXAMPLE 10

The same procedures as in Example 7 were conducted except that drying ofthe spherical particles formed from each of raw materials A and C waseffected by allowing the particles to stand in air on an evaporatingdisk at 20° C. for 24 hours. Thus, spherical zeolite catalysts havinghigh sphericity degrees and high strengths were obtained.

COMPARATIVE EXAMPLE 3

The same procedures as in Example 7 were conducted except that drying ofthe spherical particles formed from each of raw materials A and C waseffected at 120° C. for 20 minutes, thereby obtaining spherical zeolitecatalysts having high sphericity degrees. The thus-obtained catalysts,however, had strengths as as about half of those of the catalystsobtained through 20° C.--drying in Example 7.

                                      TABLE 2                                     __________________________________________________________________________                                         Example                                                                            Example      Comparative                         Example 7               8    9    Example 10                                                                            Example                __________________________________________________________________________                                                           3                      Raw material A   A   A   C   C   C   A    A    A   C   A   C                  Drying temperature, °C.                                                             80  50  20  80  50  20  20   20   20  20  120 120                Drying time, hr                                                                            0.33                                                                              0.66                                                                              1   0.33                                                                              0.66                                                                              1   1.5  2    24  24  0.33                                                                              0.33               Product yield, wt %                                                                        98  98  98  98  98  98  98   98   98  98  98  98                 Average particle                                                                           1.5 1.5 1.5 1.5 1.5 1.5 1.5  1.5  1.5 1.5 1.5 1.5                diamter, mm                                                                   Average strength, kg                                                                       1.9 2.5 2.8 5.4 5.8 6.1 2.8  2.2  2.5 5.6 1.4 3.2                Average sphericity                                                                         1.010                                                                             1.008                                                                             1.010                                                                             1.012                                                                             1.010                                                                             1.011                                                                             1.008                                                                              1.005                                                                              1.007                                                                             1.007                                                                             1.008                                                                             1.008              degree                                                                        __________________________________________________________________________     ##STR4##                                                                      ##STR5##                                                                     ?                                                                              ##STR6##                                                                     ?                                                                         

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

What is claimed is:
 1. An apparatus for producing a spherical zeolitecatalyst which comprises:dropping means having at least one opening of acircular cross section for feeding a zeolite-containing alumina sol to areactor, impulse generating means for applying knocks to the droppingmeans to form spherical droplets of the zeolite-containing alumina sol,an impulse generating means regulator for regulating the strength of theknocks and the intervals between the knocks, a reactor, where thespherical zeolite catalyst is formed, having an upper part and a lowerpart, where the upper part of the reactor contains an oil phase whichreceives the zeolite-containing alumina sol from the dropping meanshaving at least one dropping opening and where the lower part of thereactor contains an aqueous alkaline solution, with an interface betweenthe oil phase and the aqueous alkaline solution, and outlet means at thelower part of the reactor to withdraw the spherical zeolite catalyst;wherein the impulse generating means gives constant strength knocks tothe at least one dropping opening at regular time intervals to form soldroplets having constant diameter.
 2. An apparatus as claimed in claim1, wherein said dropping opening has a diameter of from 0.5 to 3 mm. 3.An apparatus as claimed in claim 1, wherein said reactor has a spout forjetting the oil phase or aqueous alkaline solution thereinto, said spoutserving to shake the interface between the oil phase and the aqueousalkaline solution.
 4. The apparatus of claim 1, further comprising meanslocated in the lower part of the reactor to shake the interface..
 5. Theapparatus of claim 4, wherein the means to shake the interface comprisesmeans to remove aqueous solution from the lower part of the reactor andmeans to jet the thus removed aqueous alkaline solution in the proximityof the interface to thereby shake the interface.
 6. The apparatus ofclaim 1, further comprising means located in the upper part of thereactor to jet the oil phase to thereby shake the interface.
 7. Theapparatus of claim 1, wherein said impulse generating means is operatedby air pressure.
 8. The apparatus of claim 1, wherein said impulsegenerating means is operated by an electrical motor.
 9. The apparatus ofclaim 1, wherein said impulse generating means is operated by magneticforce.